The Development of Gas Sensors Based on Multivalent Cation Conducting Solid Electrolyte

氮氧化物是造成大气污染的有毒气体，抑制氮氧化物向大气中的排放是一个迫切的问题。为了有效地抑制NOx气体，需要在每个排放位置处对NOx气体进行现场感测，并且开发具有小尺寸、高灵敏度和高选择性的实用智能NOx气体传感器是非常重要的。本研究以三价Al^&lt;3+&gt;导电固体电解质和O^-<2->阴离子导电氧化钇稳定氧化锆（YSZ）为基础，以KNO_2掺杂的Gd_2O_3固溶体为辅助电极，研制了一种新型的氮氧化物气体传感器。该传感器在450℃下对NO的检测符合理论Nemst关系，对NO浓度变化的响应时间在15 min以内。该传感器在理论上与NO气体检测的情况类似，也能对NO_2气体作出响应。此外，由于即使混合气体中的NO量的比率改变，传感器输出的总NOx气体（NO + NO_2）浓度为2000 ppm，因此发现本发明的NOx气体传感器能够检测环境大气中的总NOx气体浓度。<2->KNO_2掺杂的Gd_2O_3固溶体辅助电极是一种智能型NOx气体传感器，不仅可以检测单个NO和NO_2，而且可以检测总的NOx气体。由于该传感器即使在高温下也具有高的热稳定性和化学稳定性，因此极大地期望本发明的NOx气体传感器在每个NOx气体排放场所的实际应用。

Nitrogen oxides are toxic gas species which cause air pollution, and the suppression of Nox gas emission into ambient atmosphere is an urgent issue. For an effective suppression, the on-site sensing of Nox gas at every emitting site is necessary and the development of a practical smart Nox gas sensor with a small size, a high sensitivity and a high selectivity is greatly important. In this research, we newly developed a Nox gas sensor based on trivalent Al^<3+> conducting solid electrolyte and O^<2-> anion conducting yttria stabilized zirconia (YSZ) with a water insoluble auxiliary electrode of the KNO_2 doped Gd_2O_3 solid solution.The present Nox gas sensor shows a high sensing performance according to the theoretical Nemst relationship for the NO detection at 450℃ and its response time for Nox gas concentration variation was within 15 min. On the other hand, the sensor can also respond to the NO_2 gas theoretically similar to the case for the NO gas detection. Furthermore, since the sensor outputs for total Nox gas (NO + NO_2) concentration of 2000 ppm were constant even if the ratio of NO amount in mixed gas changed, the present Nox gas sensor was found to be able to detect the total Nox gas concentration in the ambient atmosphere.In conclusion, the present sensor based on both divalent Al^<3+> and divalent O^<2-> conducting solid electrolytes with water insoluble auxiliary electrode of the KNO_2 doped Gd_2O_3 solid solution was found to be a smart NOx gas sensor which can detect not only individual nitrogen oxides of NO and NO_2 but also total NOx gas. Since the sensor also possesses both the high thermal and chemical stabilities even at elevated temperatures, the practical application of the present NOx gas sensor is greatly expected at every NOx gas emitting site.